We disagree that Lady Macbeth understands herself but not Macbeth because it is actually the opposite. Lady Macbeth understands Macbeth because she is able to manipulate him in to doing what she wants. She doesn't understand herself because at first the murders were her idea but then she winds up killing herself because she can't deal with the guilt.


Macbeth- Shakespeare Act 1 Scene 7 p 43 line 56
When you durst do it, then you were a man;And to be more than what you were, you would Be so much more the man. Nor time nor place Did then adhere, and yet you would make both. They have made themselves, and that their fitness now does unmake you.

Macbeth- Shakespeare Act 2 Scene 3 p 61 line 85
A little water clears us of this deed. How easy is it then! Your constancy Hath left you unattended. Knock. Get on your nightgown, lest occasion call us And show us to be watchers. Be not lost So poorly in your thoughts.

Macbeth- Shakespeare Act 5 Scene 1 p 163line 37
Out, damned spot, out, I say! One. Two. Why then, ‘tis time to do ‘it. Hell is murky. Fie, my lord, fir, a soldier and afeard? What need we fear who knows it, when none can call our power to account? Yet who would have though the old man to have had so much blood in him?

Macbeth- Shakespeare Act 5 Scene 1 p 163 line 53
Here’s the smell of the blood still. All the perfumes of Arabia will not sweeten this little hand. O, O, O!

Out, damned spot, out, I say! One. Two. Why then, ‘tis time to do ‘t. Hell is murky. Fie, my lord, fie, a soldier and afeard? What need we fear who knows it, when none can call our power to account? Yet who would have thought the
old man to have had so much blood in him?”
p 163 Act 5 Scene 1 line 37

“The Thane of Fife had a wife. Where is she now? What, will these hands ne’er be clean? No more o’ that, my lord, no more o’ that. You mar all with this starting.”
p 163 Act 5 Scene 1 line 44

Conclusion
Lady Macbeth could not understand herself, but she did understand her husband Macbeth. She kept telling Macbeth to kill King Duncan, and when he was doubting it she told him he was not a man. In the end Macbeth ended up being the bad guy and he killed the king, and Lady Macbeth ended up feeling bad and she killed herself because she could not deal with the guilt that she felt.